An electron beam recording apparatus (EBR) is used to manufacture an original disc for producing optical information recording medium, optical-magnetic information recording medium, phase-change information recording medium, and magnetic information recording medium. An electron beam recording apparatus is also used to form wiring pattern(s) for arranging integrated circuit elements. In use, an electron beam recording apparatus applies a converged electron beam to a recording object such as an original disc to form a recording pattern thereon.
When information is to be recorded in optical information recording medium (such as optical disc), it is necessary to prepare an original disc to record in its concave or convex tracks (groove tracks or land tracks) rotation control information such as wobbling signal or the like for controlling the rotation of an optical disc or address information needed for searching position during data recording. When concave-convex pattern corresponding to the signals is to be recorded in an original disc, a conventional method is to apply a converged beam spot to a recording surface. However, in order to form a fine (small) track pitch to satisfy a high density recording required by an optical recording medium, there has been in use another recording method which utilizes an electron beam having a smaller spot size than a laser beam and capable of obtaining a high recording resolution.
The following Patent Document 1 has disclosed an electron beam recording apparatus capable of producing a high density original (optical) disc. Such an electron beam recording apparatus is suitable for recording signals in concentric tracks of an original disc, while the apparatus itself comprises a rotation driving section which supports and rotates an original disc having formed thereon a resist layer, an electron beam emitting section for deflectably applying an electron beam to an original disc to form a beam spot thereon, and a relative movement driving section for relatively driving in parallel the rotation driving section and the beam spot in the radial direction of the original disc.
However, the above-mentioned electron beam recording apparatus requires its electron beam to be adjusted prior to its recording operation. This is because an electron beam is apt to receive an influence from a magnetic field of a surrounding environment. When a beam vibrates due to an influence from a magnetic field, a recording precision will drop. On the other hand, it is impossible to branch an electron beam like a laser beam during a recording operation to monitor a beam position and a beam state while the recording is going on. Moreover, when an electron beam is adjusted, it is necessary to measure a change in beam position, a size of a focusing spot of the beam, so as to adjust the beam at a time of recording in accordance with a measurement result.
FIG. 1 shows a conventional system for measuring a beam displacement during an electron beam measurement prior to a recording operation. As shown, a knife edge N is disposed in a spot position of a converged electron beam E so as to block a half of the beam spot. An electric current arriving at a Farady cup F through the knife edge N is amplified by a current amplifier A and then outputted to an oscilloscope O, thereby measuring a beam displacement with respect to the electron beam E.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-367241.